1. Field of the Invention
This invention relates to shaping heat softened glass sheets, and in particular, to shaping pairs of glass sheets to a nonuniform curved configuration by combination of preliminary gravity sag bending on a ring-type outline mold, and final press bending between a pair of vertically aligned full surface press faces.
2. Technical Consideration
One common technique for shaping a glass sheet is to support the sheet on an outline bending mold having a shaping rail with an upper surface having elevational contours corresponding to the final desired shape of the glass sheet. The glass sheet is heated to its heat softened temperature and sags by gravity to assume the desired configuration. This technique is particularly well suited for simultaneously shaping two sheets of glass, or doublets, that will be used as the inner and outer plies of conventional laminated glass, for example a windshield.
As the glass sheet configurations become more complex and include deeper bend sections, the shaping rails may be segmented and made to pivot from an open rigid glass sheet supporting position to a closed heat softened glass sheet supporting position. In the closed position, the shaping rails assumed the desired elevational contours of the glass sheet to be shaped slightly inboard of its perimeter.
In addition, pressing molds may be used to shape glass doublets to complex and complicated configurations by pressing the glass sheets batween a pair of aligned full surface press faces. When pressing molds are used in conjunction with an outline mold, the lower mold generally moves upward through the rail of the outline mold, lifting the glass sheet off of the outline mold and pressing it against a complementing upper mold. Since the shaping surface of the lower mold must move through the outline mold, only those portions of the glass within the boundary of the outline mold are pressed. The circumferential area of the glass sheet contacts only the upper press face of the mold. As a result, the glass sheets are not pressed to shape out to their peripheral edge.
It would be advantageous to provide a bending arrangement wherein glass sheets can be preliminarily shaped on an outline bending mold and pressed between a pair of full surface bending molds to impart a final configuration wherein the full surface molds press the glass sheets along selected peripheral areas.